With the invention of powered land vehicles in the late nineteenth century, steering control became a serious design consideration. The use of a wheel for land vehicle steering originated in nautical applications in the early 1700s when the “whipstaff” helms used until then failed to provide sufficient rudder angles as the ships gained size and weight. Whipstaff helms were replaced by wheels that operated the rudder using rope, drum and pulley systems. Early automobiles utilized a tiller for steering. However, in 1894 a Panhard et Levassor vehicle was fitted with the first known adaptation of a steering wheel, starting the trend that has been carried on to the present time.
The steering wheels of the early twentieth century were large and required significant strength to effect the necessary driving control, as early cars were quite heavy. A brief interlude in wheel use took place in the first decade when electric cars made their appearance. Because of their light weight they could use a relatively long horizontal arm mounted to a vertical spindle and pushed to turn left or pulled to turn right. However, the advent of Henry Ford's model T in 1908, with its advanced metallurgy, engineering, simplicity and light weight, cemented the steering wheel's prominence.
Power steering replaced manual steering in the mid twentieth century, alleviating the difficulty of turning a steering wheel especially at low driving speeds. However the steering ratio, i.e., the number of turns of the steering wheel needed to adjust the direction of the front wheels of an automobile through a given angle, underwent little if any change. Even in a modern, automobile with power steering, the steering wheel typically rotates about 2.5 full turns (90°) lock to lock, adjusting the angle of the front wheels of the automobile through about 90° (45° to either side of a neutral position).
In modern automobiles as in early manually steered automobiles, because of the approximately 900° range of rotation of the steering wheel, execution of a turn typically requires a complex “hand over hand” manipulation in which the driver's hands alternately release the wheel and are moved from one position to another. (The term “hand over hand” is also intended to encompass any of several variations of an intermittent, repeated, steering manipulation, such as one in which, while a first hand firmly grips the wheel, the second hand is slid toward the first hand, and then grips and rotates the wheel, moving away from the first hand causing the rim of the wheel to slide relative to the first hand while the grip of the first hand on the wheel is loosened.) Although the skill to carry out these movements can be acquired by most people, the manipulation is not necessarily intuitive, and for many people it takes a significant amount of time to become comfortably accustomed to steering wheel operation.
Variable gain, speed-dependent, steering controls have been proposed, and some examples are described in the following United States patents and published patent applications:
6,279,695Bohner et al.6,308,122Nishizaki et al.6,367,577Murata et al.6,442,462Nishisaki et al.6,799,105Stout et al.6,886,656Fujioka et al.6,899,196Husain et al.7,004,279Shitamitsu et al.7,174,987Husain7,363,134Mitsuhara7,604,089Hidaka et al.7,837,004Yasuda7,860,624Kubota et al.7,913,803Hidaka8,036,793Auguet et al.2010/0070137Yamaguchi et al.2011/0313620Mukai et al.Despite the development of these and other sophisticated vehicle steering control systems, none of them offers a satisfactory alternative to “hand over hand” steering wheel manipulation.
Some efforts have been made to develop high gain steering systems, i.e., systems in having a high ratio of the angle of the road engaging wheels to the movement of the steering control, e.g., a “joy stick”. However, in most cases, the ratio was constant. In others, the ratio was adjustable. Here again, although the systems did not require hand over hand manipulation, they did not supply a satisfactory alternative.